This invention relates to set-up of forwarded calls in a system wherein closed user groups are defined.
It is known in telecommunication systems to define closed user groups (CUG), e.g. defined by the staff of a company or by a certain circle of friends. The services of a closed user group may be different and e.g. cheaper than normal calls.
The use of a closed user group in a telecommunication system is described in the GSM 02.85 specification published by the ETSI (European Telecommunications Standards Institute). In accordance with the specification, a subscriber belonging to a closed user group may have various subscriber options defined for himself which tell what kinds of calls the subscriber may receive or make. These subscriber options are
1. CUG calls only; the subscriber may set up calls only with subscribers of his own CUG group,
2. Access for CUG and incoming calls; the subscriber may set up calls with subscribers of his own CUG group and also receive calls coming from outside his own CUG group (IA, Incoming Access),
3. Access for CUG and outgoing calls; the subscriber may set up calls with subscribers of his own CUG group and may also make calls going outside his own CUG group (OA, Outgoing Access), and
4. Access for CUG and outgoing and incoming calls; the subscriber may set up calls with subscribers of his own CUG group and may also make calls going outside his own CUG group and receive calls coming from outside his own CUG group (IA+O xc3x85).
In addition, restrictions within the user group may be defined for he subscriber,
1. ICB, incoming calls barred within a CUG, and
2. OCB, outgoing calls barred within a CUG.
A subscriber may belong simultaneously to several closed user groups CUG, of which one may be selected as default group, which is used in the set-up of outgoing calls, unless otherwise mentioned for the individual call.
FIG. 1 shows storing of information relating to closed user groups in a home location register HLR. A copy of the information presented in the figure is also preserved in the subscribers visitor location register VLR. An international mobile subscriber identity IMSI functions as the key to the record. A list of the basic services to which the subscriber has a right is appended to the subscriber identity. Services are distinguished from each other with the aid of basic service group codes BSGC. To the services is connected information on the closed user group CUG to be primarily used when setting up a call as well as information on OA access of outgoing calls outside the group. In the example shown in the figure, such a user group is defined for primary use in connection with speech service T11 for the subscriber, the CUG INDEX of which =1, and there is also access for outgoing calls going outside the group (OA=T). Correspondingly, in connection with fax service T62 of group 3, such a user group is used primarily, the CUG INDEX of which =2, and outgoing calls going outside the group are barred (OA=F). In connection with the PAD service (Packet Assembler/Disassembler) BA6 to be used when connecting to packet data networks at a transmission rate of 9600 bits a second, such a user group is used primarily, the CUG INDEX of which =4, and outgoing calls going outside the group are barred (OA=F).
In addition to service information and primary CUGs relating to services, the visitor location register stores a description of network-specific CUG IC (CUG Interlock Code) group attributes which are used between subscriber-specific CUG INDEX group attributes and exchanges. In the example shown in the figure, the CUG INDEX 1 of the subscriber""s user group corresponds to the network-specific CUG IC 101 symbol, while CUG INDEX 2 corresponds to CUG IC 12, CUG INDEX 3 to CUG IC 1 and CUG INDEX 4 to CUG IC 14.
FIG. 2 shows transmission of information relating to the use of a closed user group when setting up a call. In the example, a call is set up between two mobile stations MSA and MSB (MS=Mobile Station). According to the figure, the CUG user group which is to be used is distinguished between the calling mobile station MSA and the mobile switching centre MSC and a visitor location register VLR typically located in connection with the MSC, using subscriber-specific CUG INDEX information together with the subscriber identity. If in connection with the call set-up, the MSA does not separately state any CUG to be used, then that closed user group will be used which has been defined by the subscriber as the default group for this basic service. If no default group has been defined for the basic service and the subscriber does not in connection with the call set-up indicate any closed user group to be used, the call will be set up as a normal call, if the subscriber has given access to normal calls (OA).
Upon receiving the request for a call set-up, the MSC/VLR checks if the MSA has the right to set-up of the CUG call he requested. This is done with the aid of the CUG INDEX information obtained from the subscriber, with subscriber data stored in the visitor location register VLR and with a special authorisation function. The call set-up is continued, if it is found that the subscriber is so entitled.
A user group to be used in communication between mobile switching centres is identified within the user group""s network by a CUG IC identifier performing unambiguous identification. in addition, in communication between exchanges the term OA is used, which tells whether the call is allowed to be an outgoing call going outside the CUG.
When setting up a call, the calling subscriber MSA""s exchange MSC contacts the GMSCB gateway mobile services switching centre of subscriber B based on the MSISDN number (MSISDN=Mobile Subscriber ISDN) which identifies subscriber B. The GMSCB is a centre able to make SRI (Send Routing Information) enquiries to subscriber B""s home location register HLRB. In the SRI, the GMSCB sends to the HLRB the IC(A) identifier of the CUG defined by subscriber A and information on access of outgoing calls going outside the group.
FIG. 3 shows the operation of home location register HLRB. The HLRB receives the SRI enquiry (step N01) and checks whether MSB belongs to the CUG defined by subscriber A by comparing the IC(B) group symbols of subscriber B with the IC(A) group data stated by subscriber A (step N02). If it is found that subscriber B belongs to the defined user group, then IC(A)∈{IC(B)} is true, and the operation proceeds to step N03, where it is checked whether MSB has barred incoming calls within the group (ICB). If calls within the group are allowed (ICB(B) is false), a further check is made in step N04 to find out whether subscriber B has defined forwarding of the call. The call will be forwarded, if subscriber B has determined that his call is to be forwarded unconditionally to subscriber C (CFU, Call Forwarding Unconditional) or if HLR finds that the subscriber can not be reached and the subscriber has defined CFNRc (Call Forwarding on Not Reachable) to be made in such a case. If forwarding is not defined or the forwarding conditions are not met, the call set-up is continued as a CUG call (step N05). If the call is defined to be forwarded to a third subscriber (subscriber C), the CUG information (IC(A), OA(A)) is checked to find out whether forwarding of the call can be carried out (step N20).
If it is found in step N02 that subscriber B does not belong to the user group (IC(A)∉{IC(B)}) defined by subscriber A, or in step N03 that subscriber B has barred internal calls in the group, progress is made to steps N11 and N12, where it is checked whether the call can be set up as a normal call. A check is made in step N11 to find out whether subscriber A has allowed the call to go outside the group (OA(A)) and in step N12 whether subscriber B has allowed access for calls coming from outside the group (IA(B)). If each condition is fulfilled, it is checked whether the call must be forwarded to a third subscriber, that is, to subscriber C (step N13). If no forwarding is defined or if forwarding conditions are not fulfilled, the call is continued as a normal call (step N14). If forwarding of the call is defined, a check is made based on the CUG data (IC(A), OA(A)) given by subscriber A to find out whether forwarding of the call can be carried out (step N20).
If no condition of steps N11 and N12 is fulfilled, the call will be rejected (step N30).
If set-up of the call is continued without forwarding the call (steps N05 and N14), HLRB will use a PRN message (Provide Roaming Number) to request the MSRN roaming number (Mobile Subscriber Roaming Number) of subscriber B""s current visitor location register VLRB. The roaming number is used to identify the called subscriber B during the call set-up. HLRB returns the roaming number it has received together with the CUG identifiers defined by subscriber A to GMSCB, which for its part sets up a connection with the MSB mobile station through VMSCB using the roaming number as identifier.
Should HLR find in step N04 or N13 of FIG. 3 that the call is defined to be forwarded to subscriber C, a check is made of whether forwarding is possible. This functionality is shown in FIG. 4. It is checked in step B02 if subscriber B belongs to the user group defined by subscriber A. If this is not the case, an instruction is returned to GMSCB to forward the call to subscriber C using the CUG parameters (IC(A), OA(A)) defined by subscriber A, if both subscriber A and subscriber B have defined access for outgoing calls outside their CUG groups (steps B21 and B22).
If subscriber B belongs to the CUG group defined by subscriber A, it is checked whether subscriber B has barred outgoing calls inside the group (step B03). If this is not the case, an instruction is given to GMSCB to forward the call to subscriber C as a CUG call. If both subscriber A and subscriber B have defined access for outgoing calls outside their CUG groups (steps B11 and B12), the forwarded call is also allowed to go outside the group (OA, step B23). If this is not the case, the call is forwarded as a CUG call without allowing the call to go outside the group (step B13).
If subscriber B has barred calls inside the group, progress is made from step B03 to steps B04 and B05, where GMSCB is controlled to forward the call as a normal call (step B06, normal call), if both subscriber A and subscriber B have defined access for outgoing calls outside their CUG groups. If at least one subscriber has barred outgoing calls going outside the group, the call is barred (step B30).
Thus, in the forwarding leg defined by subscriber B the CUG parameters defined by subscriber A are mainly used. Based on the CUG definitions of subscriber B, the CUG definitions of subscriber A can be changed only
1. to bar outgoing calls outside the CUG group of subscriber A, if subscriber B has barred his outgoing calls going outside his own group, and
2. to set up the call as a normal call, if subscriber B has barred calls inside the CUG group defined by subscriber A, but both subscriber A and subscriber B allow outgoing calls going outside the group in question.
Having received from HLRB an instruction to forward the call, GMSCB continues to set up the call towards subscriber C based on the CUG information it has received from HLRB. FIG. 5 shows routing of the call to be set up. The call is now formed by legs 1 and 2 between the GMSCB gateway centres of subscriber A and subscriber B and by the forwarding distance formed by legs 3, 4 and 5 between GMSCB and subscriber C. Forwarding takes place in GMSCB, which is called the forwarding point. If subscriber B or subscriber C is a fixed network subscriber, no enquiry is made to the home location register for his part, because the subscriber information is then stored in the exchange of his fixed network. If supplementary service information of the subscriber is stored in an IN (Intelligent Network) connected to his exchange, the exchange must fetch the said information through an enquiry to the intelligent network.
If the subscriber has defined call forwardings to be performed in VLR such as CFB (Call Forwarding on Busy), CFNRy (Call Forwarding on No Reply) or CFNRc (Call Forwarding on Not Reachable), and VLR finds that the condition for such call forwarding is fulfilled, VLR will make the checks shown above in FIG. 4 and will continue to set up the call towards subscriber C. The forwarding point will then be that VMSCB centre, see FIG. 2, under which subscriber B is operating at the moment.
In the processing of forwarded calls the usual charging principle is that subscriber A always pays for the leg between subscriber A and the call forwarding point, while subscriber B pays for the leg between the forwarding point and subscriber C. However, CUG information defined by subscriber A is used in that leg of the call which is between subscriber C and the forwarding point defined by and paid for by subscriber B. If subscriber B and subscriber C belong to the same CUG group, it would be most natural to set up the B-C forwarding leg as a CUG call which may have more advantageous characteristics and a more advantageous price than a normal call. E.g. in cases where a calling subscriber A does not belong to the same CUG user group as subscriber B and subscriber C, the call will be set up in accordance with FIG. 6 as a normal call both over the A-B distance and over the B-C distance.
FIG. 7 shows another situation, where problems are caused by a state-of-the-art arrangement. In the figure, subscriber A belongs to user group G2, subscriber B to user groups G1 and G2 and subscriber C to user group G1. Subscriber B has defined forwarding of his calls to subscriber C as CUG calls. When subscriber A makes a CUG call to subscriber B with no access (no OA) of outgoing calls outside the group, the home location register HLRB of subscriber B checks if subscriber B belongs to the G1 user group defined by subscriber A. Since this is the case, set-up of the call is continued from forwarding point GMSCB towards subscriber C with the CUG information provided by subscriber A. A check is made in the home location register HLRC of subscriber C to find out if subscriber C belongs to the CUG group G2 defined for the call. Since this is not the case and the call is not allowed to go outside the said G2 group, set-up of the call is discontinued.
Further, in state-of-the-art systems, the type of a call is not known before the CUG checks made by the final recipient of the call. If the calling subscriber defines a CUG group for use in the call and also allows the call to go outside the group, the MSCA centre of the calling subscriber or the GMSCB centre of the called subscriber does not know if the call should be set up as a CUG call or as a normal call. For this reason, statistics on the call and charging of the call must use the name xe2x80x9cmaybe CUGxe2x80x9d for the call as regards the A-B distance.
For the reasons presented above, controlling of forwarded calls of a closed user group is difficult, especially the use of leg-based charging. The present invention aims at solving these problems. The aim is achieved with the method and equipment defined in the independent claims.
The inventive idea is to set up a forwarded call using a service of a closed user group always legspesifically. Hereby such user group information can be used for each leg which is defined by the subscriber explicitly for the concerned leg. The user group information defined by a calling subscriber A is used on that leg of the call which is between subscriber A and the call forwarding point. The user group information defined by the called subscriber who has forwarded the call is used between the forwarding point and the subscriber who is the forwarding target.
In one embodiment, the network element, such as a home location register, maintaining subscriber information of the subscriber who has activated a conditional or an unconditional call forwarding, is adapted in connection with the call set-up to return the user group information defined by the subscriber for the forwarding leg. In addition, the exchange or centre functioning as the call forwarding point is adapted to continue set-up of the call based on the user group information it has received for the forwarding leg towards the subscriber who is the forwarding target.